A lamp unit of said type can in principle be used in a multiplicity of single-ended lamps. However, the main field of application is most likely to be in lamp units for vehicle headlights. A lamp unit for such motor vehicle headlights is described for example in EP 1 605 490 A2 and DE 10 2005 009 902 A1.
In these known solutions the lamp unit has a discharge lamp, such as is marketed for example under the product name “Xenarc™”. Said high-pressure discharge lamp has a single-part or multipart lamp base by way of which it can be inserted into a holder of a reflector of a motor vehicle headlight. In order to align the lamp in the reflector and prevent incorrect installation of different lamp types, one or more referencing and coding recesses are embodied on a referencing ring of the base, which recesses cooperatively interact with corresponding projections on the holder of the reflector in order to ensure that the lamp can only be inserted at a predetermined relative position with respect to the holder. Said referencing means furthermore prevents lamps of an unapproved type from being used in a motor vehicle headlight.
In the conventional solutions a plurality of radially projecting supplementary elements which form part of the headlight are additionally arranged on the base of the high-pressure discharge lamp, with which mechanical components, for example clips, brackets, coupling cages or the like come into engaging contact in order to fix the base at a defined position in the holder of the reflector.
A disadvantage with said solutions is that firstly lamp units of this type are relatively complex in terms of their structure, since the additional components must be provided for ensuring correct positional fixing. Secondly, the assembly overhead is increased due to the attachment of the additional components.